In radiography, the radiographic films are exposed in radiographic cassettes consisting substantially of a base element, generally impermeable to X-rays, and an upper element generally permeable to X-rays, which are joined together by a vertical perimetral element so as to form a container having an essentially flat parallelepiped shape. Said flat horizontal upper and base elements and said vertical element have the minimum dimensions necessary for containing a radiographic film of a certain format disposed between intensifying screens fixed to said upper and base elements. Said screens are uniformly pressed against the film so as to ensure good uniform contact with the film, as known to experts of the art. Said base element is generally constructed in the form of a lid hinged along the rear edge of the cassette.
When such cassettes are opened in an automatic loading and unloading apparatus (especially when the cassette is disposed substantially vertically, as in the case of the apparatus of the applicant), it is normally necessary for the film to separate from a predetermined screen chosen from the base screen and upper screen contained in it (in the case of the apparatus of the applicant, the film must separate from the upper screen). In the absence of any means for controlling the separation of the film from the screens during the opening of the cassette, the film can separate randomly from one or other of said screens, and thus in the past springs have been used in order to cause the film to separate under control, as required. However, such screens can lead to loss of adhesion and loss of sharpness of the image around the zone occupied by them, and easily deteriorate with time.